Biomedical Engineering Reference
In-Depth Information
i
a
b
e
ii
iii
c
Slow speed
DC motor
Cap
“Raft”
Big glass jar
(PS, PS-AA, epoxy)
Polymer solution
(PS, PS-AA, epoxy)
iv
Mechanical
release
d
v
f
g
h
i
100 µm raft
72 hrs
eGFP
FIGURE 5.30
Micromolded.rafts.for.cell.culture..(From.Yuli.Wang,.Colleen.Phillips,.Wei.Xu,.Jeng-
Hao.Pai,.Rahul.Dhopeshwarkar,.Christopher.E..Sims,.and.Nancy.Allbritton,.“Micromolded.arrays.for.
separation.of.adherent.cells,”.
Lab Chip
.10,.2917-2924,.2010..Reproduced.with.permission.from.
The.Royal.Society.of.Chemistry.)
What if the cells were not adherent? David Gracias' laboratory at Johns Hopkins University
has developed microactuators that change shape in response to thermal or chemical changes.
he microactuators can take the shape of microcages (
Figure 5.31
) or microgrippers when they
fold up. he actuators contain trilayer joints or hinges composed of photoresist and a stressed
bimetallic thin ilm. he assembly of the microcages is thermally triggered, without the need for
any external connections, so that the highly parallel self-loading of glass beads, ibroblasts, and
tadpole shrimp embryos could be demonstrated.
5.3.9 Microdroplet Cultures and Assays
And how about using
dissimilar
luids to conine the cells—that is, conining the cells into
oil-surrounded aqueous droplets, which can be produced at very fast rates in microchannels?
Rustem Ismagilov's group at the University of Chicago was the irst to pioneer what are now
intensive investigations in this direction. Oil-suspended droplets illed with single bacterial cells
could be grown and split for parallel tests (cellulase assay, cultivation, cryopreservation, and
Gram staining); the plugs could be deposited on a plate for luorescent in situ hybridization
(
FISH
) or on an agar plate for culture (
Figure 5.32
).
To generalize this concept to mammalian cells, the cells will need to be pre-encapsu-
lated in beads made of a matrix that supports cell attachment. Still, a team from RainDance
Technologies (Lexington, MA) and Harvard Medical School led by Michael Samuels has
